Viability of Dirac phase leptogenesis

TL;DR

This paper explores whether the Dirac CP phase and mixing angle _{13} in neutrino oscillations can solely account for the universe's matter-antimatter asymmetry through leptogenesis, highlighting conditions for viability.

Contribution

It demonstrates that -leptogenesis is viable in the degenerate heavy neutrino spectrum scenario and derives testable conditions linking _{13} and neutrino mass scale.

Findings

-leptogenesis is viable with degenerate heavy neutrinos.

Hierarchical heavy neutrino spectrum makes -leptogenesis unlikely.

Future experiments could test or rule out -leptogenesis scenarios.

Abstract

We discuss the conditions for a non-vanishing Dirac phase \delta and mixing angle \theta_{13}, sources of CP violation in neutrino oscillations, to be uniquely responsible for the observed matter-antimatter asymmetry of the universe through leptogenesis. We show that this scenario, that we call \delta-leptogenesis, is viable when the degenerate limit (DL) for the heavy right-handed (RH) neutrino spectrum is considered. We derive an interesting joint condition on \sin\theta_{13} and the absolute neutrino mass scale that can be tested in future neutrino oscillation experiments. In the limit of hierarchical heavy RH neutrino spectrum (HL), we strengthen the previous result that \delta-leptogenesis is only very marginally allowed, even when the production from the two heavier RH neutrinos is taken into account. An improved experimental upper bound on \sin\theta_{13} and (or) an account of quantum kinetic effects could completely rule out this option in the future. Therefore, \delta-leptogenesis can be also regarded as a motivation for models with degenerate heavy neutrino spectrum.